Crystallization Mechanism and Kinetics of BaO-Li2O-ZrO2-SiO2 Glasses

DTA and SEM were used to determine the influence of the addition of BaO on the crystallisation mechanism of Li2O-ZrO2-SiO2 systems. As the concentration of BaO in the samples increased, a transition occurred in the predominant crystallisation mechanism, which passed from superficial to volumetric. To determine the maximum nucleation rate, the crystallisation kinetics of the sample containing 20 mole% BaO, which showed the most uniform crystallisation, were studied by counting the nuclei with an image analyser. The first nuclei appeared at the first endothermic inflection point (at the start of Tg, at 440 C), while the maximum number of nuclei was counted at the midpoint of the glass transition region (446 C). These results are similar to those observed for other materials that crystallise in volume, and confirm SEM data. 7 refs.